I just found out by chance that your forum cms or the custumization of it does not like a turned off user agent. I was using firefox user agent switcher addon with a setting that sends an empty or no user agent when I tried to reply to this post. I received this message:
We are currently unable to serve your request
We apologize, but an error occurred and your request could not be completed.
This error has been logged. If you have additional information that you believe may have caused this error please report the problem here.
Turning on the default user agent solved the problem.